Drinking vessels such as cups and mugs come in a wide variety of types, including china mugs with replaceable lids, traditional drinking mugs of various shapes, sizes and materials, including beer steins With hinged lids, and disposable paper and plastic cups.
In the case of china mugs with lids, the lid serves to stabilize the temperature of the contents, and to prevent spillage and the entry of foreign or contaminating matter, and is removed when one wishes to drink, making the lid susceptible to loss and breakage.
The use of traditional drinking mugs has been superceded in significant measure by disposable cups of papers and styrofoam, which frequently include tops having tear tabs to provides drinking access. The widespread use of such disposables forms a part of our present ecological problems.
In addition to the many varieties of removable, disposable covers having a skirt portion which grip the outside of the cup rim, there are plastic covers with tear-off segments that form a drinking aperture, and various other receptacle variants, as illustrated in the following listed Canadian patents:
945,940, April 1974, Rathbun; PA1 1,012,928, June 1977, Albert et al.; PA1 1,056,332, June 1979, Douglas; and PA1 1,139,716, January 1983, Philip
In the case of beer stein containers With hinged lids, these are cumbersome and awkward to use, and little suited to use with ordinary beverages such as cold and hot drinks.